In recent years, various optical disc media are used as information recording media. An optical disc device is used to read information recorded on such an optical disc medium. The optical disc device includes an optical pickup which irradiates the optical disc medium with light to detect reflected light from the optical disc medium. The optical disc device controls a drive system for relatively moving the optical pickup with respect to a surface of the optical disc medium to move the optical pickup to a position at which the information can be read. In this manner, the optical disc device reads the information from the optical disc medium.
When the optical disc device controls respective portions such as the optical pickup and the drive system to read information from the optical disc medium, various control parameters are set regarding the control. One example of those control parameters is a parameter regarding spherical aberration correction of an objective lens (hereinbelow, referred to as SA parameter). For example, inside the optical pickup, there is provided a collimator lens in order to correct the spherical aberration of the objective lens used for focusing light onto the optical disc medium. Then, by appropriately adjusting the position of the collimator lens according to the set value of the SA parameter, the spherical aberration of the objective lens is corrected, with the result that the light from the objective lens can be focused onto the optical disc medium with high accuracy. As described above, the optical disc device can be improved in accuracy of reading information from the optical disc medium by setting appropriate values for the control parameters such as the SA parameter, and controlling the respective portions of the device under an operation condition corresponding to the set values.
The values to be set for those control parameters vary depending on the type, the individual variability, and the like of the optical disc medium being a reading target. Thus, when an optical disc medium is newly set inside the device, the optical disc device first performs processing of adjusting the control parameters before starting the reading of information (for example, see Patent Literature 1). Specifically, this adjustment processing involves the following control. That is, the optical disc device first changes the set value of the control parameter within an assignable range, and attempts the reading of information from the medium by setting several set values, thereby evaluating the corresponding information reading accuracy. Then, by using the evaluation value of the reading accuracy obtained for each of the plurality of set values, such a set value (adjustment value) of the control parameter that can improve the information reading accuracy is calculated, and the calculated value is set as the value of the predetermined control parameter.